File extension
.cab
MS CAB file format with source
.cab files are Microsoft Cabinet archives: a compressed container used throughout Windows for installers, drivers, and system components, supporting multiple compression methods and multi-cabinet spanning.
Known meanings
Formats and reference material for .cab
MS CAB file format with source
MS CAB file format with source
Details
Format notes
Microsoft Cabinet (CAB)
The Cabinet format is Microsoft’s native compressed archive, used extensively in
Windows software distribution: application setups, device driver packages,
Windows Update payloads, and the internals of other package formats all rely on
.cab. A cabinet stores one or more files, compressed, together with a
directory describing them, and starts with the signature MSCF.
Internally a cabinet is organized into “folders” (compression units) and files. Each folder holds a compressed data stream, and files are stored as ranges within a folder, so several small files can share one compression context. CAB supports the MSZIP (a DEFLATE variant), LZX, and Quantum compression methods, with MSZIP and LZX being the ones in common use.
Spanning And Related Formats
Cabinets can span multiple files: a file too large for one cabinet, or a set
split for distribution across media, continues into subsequent numbered
cabinets that are logically read as a set. The CAB structure also underlies
self-extracting installers and is referenced by other Microsoft packaging
formats, so a .cab is frequently encountered embedded inside larger installers
rather than on its own.
Preservation And Security Notes
The common media type is application/vnd.ms-cab-compressed, and open tools such
as cabextract can read cabinets on non-Windows systems. As a compressed
container feeding software installation, untrusted cabinets warrant the usual
archive precautions — validated paths, bounded expansion, and integrity checks —
and should be treated as potential carriers of executable content.
Further Reading
- Microsoft Cabinet format specification:
https://learn.microsoft.com/previous-versions/bb417343(v=msdn.10) - cabextract project:
https://www.cabextract.org.uk/